The Restoration Advisory Board (RAB) heard a presentation on PCB health effects at its April 1, 1997 meeting. The presentation was made by the Navy Environmental Health Center, Norfolk, Virginia. Several personnel assigned to the Health Center were in Alameda interviewing Navy Firefighters as part of a dose reconstruction project. The dose reconstruction project is aimed at determining the amount of PCBs that a firefighter may have been exposed to while performing activities in contaminated areas of the Naval Air Station. A firefighter present at the meeting welcomed the involvement of the Health Center but expressed concern that the NAS command had already reached a decision that firefighters were not at risk, even before the Health Center's evaluation was performed.
The Navy has proposed to perform a dose reconstruction project for Navy firefighters to determine if the exposure to chemicals at contaminated sites represented a potential health risk. Similar to the firefighters, residents have been routinely exposed to chemical hazards from chemical waste disposal, uncontrolled hazardous waste sites, permitted air emission sources, fugitive air emissions and emissions from ship, aircraft, and vehicles. In some instances these exposures may have included deposition of metals or other non-volatile contaminants on property throughout West Alameda.
Should the Navy perform an evaluation to determine if their operations from 1939 to 1997 resulted in potentially unacceptable health risk to local residents? Does it make sense to cleanup Navy property if cleanup of pollution the Navy deposited on surrounding property is not performed?
A Human Restoration component to base cleanup is important, but is not currently being considered. A dose reconstruction project would be a first step in identifying and removing a real or perceived pollution burden from West Alameda.
The US EPA released a report entitled "PCBs: Cancer Dose-Response Assessment and Application to Environmental Mixtures," that indicates the Navy needs to reevaluate the way it has investigated and determined cleanup goals for PCB contaminated sites. A principal finding of the EPA report was similar to what the Agency for Toxic Substance and Disease Registry advised:
"It is important to recognize that the PCBs to which people may be exposed are likely to be different from the original PCB source because changes ..in the environment and differential biological metabolism and retention. Because of this concern, current data are considered inadequate to differentiate between the toxicity and carcinogenity of environmental PCB mixtures with any reasonable degree of confidence."
In short the toxicity of PCBs mixtures in commercial use is lower than the toxicity of PCBs mixtures found in environment due to old spills.
According to the Environmental Protection Agency report:
The EPA report discusses the higher incidences of cancer reported in studies of workers exposed to PCBs. and notes "..PCBs also have significant ecological and human health effects other than cancer, including neurotoxicity, reproductive and developmental toxicity, immune system suppression, liver damage, skin irritation, and endocrine disruption."
According to the Navy Health Center:
"Some workers exposed to PCBs in the workplace over a long period of time developed a condition known as chloracne. Chloracne is a skin condition similar to the acene teenagers get. Chloracne goes away after exposure to PBCs stops. PCBs are considered probable human cancer causing agents by most public health authorities. This classification is based entirely on studies with laboratory animals. Increased amounts of cancer have not been observe in workers with a history of PCB exposureÓ"
The US Environmental Protection Agency and State of California use the following formula to estimate the risk of cancer or other health problems:
Some chemicals are more dangerous than others. The Response Factor is a measure of this difference in how our bodies will react to different chemical doses (similar to the difference in response to different doses of medicine). Response Factors are determined largely from the results of laboratory tests on animals. Accepted values for response factors called cancer-slope factors, and chronic reference doses, are published for common environmental contaminants by the US EPA and State of California.
Determining the Chemical Dose is the principle goal of a risk assessment. The Chemical Dose must be related to contaminant concentrations in soil, water, air, or food through different exposure scenarios.
| CONTAMINATED MEDIUM |
Pathways into your body for RESIDENTIAL LAND USE | Pathways into your body for INDUSTRIAL LAND USE | |
| GROUNDWATER | Drinking water Breathing evaporated chemicals Absorb through skin (bathing) |
Drinking water Breathing evaporated chemicals Absorb through skin (bathing) |
|
| SURFACE WATER | Drinking water Breathing evaporated chemicals Absorb through skin (bathing) Ingestion during swimming Eating contaminated fish |
Drinking water Breathing evaporated chemicals Absorb through skin (bathing) |
|
| SOIL | Eating, smoking, hand-to-mouth contact with dirty hands Breathing dust Breathing evaporated chemicals Breathing evaporated chemicals accumulated in a building Chemicals in soil leach to groundwater Eating contaminated plants, meat, or dairy products Absorb through skin (bathing) Ingestion during swimming Eating contaminated fish |
Eating, smoking, hand-to-mouth contact with dirty hands Breathing dust Breathing evaporated chemicals Breathing evaporated chemicals accumulated in a building Chemicals in soil leach to groundwater Breathing dust caused by trucks and heavy equipment Absorb through skin (bathing) |
Benzene is a cancer causing chemical that is found in gasoline. To determine the cleanup level for a gasoline spill that impacts a drinking water supply a cleanup level for benzene in drinking water is determined.
Acceptable Risk = one additional case of cancer per one million people = 0.000001
Response (Oral Cancer Slope) Factor = 0.029 kg-day/mg (from laboratory animal studies)
therefore the acceptable lifetime dose of benzene is
Acceptable Dose = (Acceptable risk)/(Response or Oral Cancer Slope Factor)
= (0.000001/0.029) = 0.0000345 mg Benzene/kg body weight per day
The acceptable dose must be related to the concentration of benzene in drinking water using the following factors provided by the EPA,
Body Weight = 70 kg (154 pounds)
Averaging Time = 70 years (lifetime)
Average Drinking Water Intake = 2 liters/day (0.53 gallons/day)
Exposure Frequency = 350 days/year
Exposure Duration = 30 years
|
|
(acceptable dose)(body weight)(lifetime) (exposurefrequency)(exposure duration)(drinking water intake) |
|
| = | 0.003 mg Benzene/Liter of drinking water | |
| = | 3 parts-per-billion (ppb) |
Therefore the cleanup concentration for benzene in drinking water would be 3 ppb.
Risks from all contaminants are combined. The total risk would be the risk from contaminant A plus the risk from contaminant B, etc. As a result, cleanup levels for individual pollutants may be lower at a cleanup site where multiple contaminants are present.
Soil and water tests can determine the presence of a pollutant only if it is at a concentration above the lab tests detection limit. Some chemicals could be determined to represent an unacceptable health risk at levels below detection limits.
Human response factors are generally estimated from lab tests on animals. As a result, acceptable levels of chemicals in water have been developed to protect fish species. These levels are considered in risk assessments to ensure that wildlife, as well as humans, are adequately protected from chemical related health problems.